HEY! I found it! A tiny footnote on Page 3 of the Tools for Tyros manual says that the Voice Editor and the File Utility programs are stand-alone applications OR OPT applications. That means you can open these programs from within a sequencer like Cakewalk Sonar 2.0. I assume that would also mean that the Tyros voice editor has or is also a Cakewalk instrument definition file. That's news.

Now how hard would it have been for Yamaha to just say that their software is compatible with popular sequencer programs like Sonar 2.0 in the Tyros owner's manual?